Physics vs. Code: Why Google’s ‘Quantum Money’ Could Make Blockchain Obsolete

For more than a decade, the world of digital currency has been built on a single foundation: the blockchain.

This complex system, based on distributed ledger code, was a revolutionary approach to creating digital scarcity and preventing counterfeiting.

But now, Google researchers are exploring a concept that could bypass it entirely, securing money not through a chain of code but through the fundamental laws of physics.

This new research in “quantum money” offers an alternative to cryptocurrencies such as Bitcoin and it targets the very problem that a blockchain was designed to solve.

If successful – a big if, since it presupposes advanced quantum computing – it will effectively obviate the need for a core technology of a blockchain, which represents a fundamentally different path towards a secure digital future.

In a new to studydoubled “Anonymous Quantum Tokens with Classic Verification,“ researchers from Google Quantum AI, the University of Texas at Austin, and the Czech Academy of Sciences have advanced a decades-long idea for a theoretical currency secured by the immutable laws of quantum mechanics.

The paper outlines a system where money is not just data on a ledger, but a unique quantum object whose integrity is guaranteed by the fabric of reality itself.

The Uncopyable Dollar

The concept is based on one of the strangest and most powerful principles in physics: the “No cloning theorem.”

This law states that it is impossible to create a perfect and independent copy of an unknown quantum state. While a chain of data on a computer can be copied endlessly, a quantum state cannot.

“If you had a $1 bill that was actually a quantum state, you could prove, based on the properties of quantum mechanics, that copying such a state is impossible,” said Dar Gilboa, a Google Quantum AI researcher and co-author of the study. Decrypt. “You can only succeed with minimal probability.”

In this system, forgery is not only computationally difficult, as in Bitcoin; it is physically forbidden.

Replaced the ledger with physics

This is where the technology becomes a direct threat to the blockchain model.

The primary function of a blockchain is to prevent “double spending” without a central authority. It does this by creating a massive, public and immutable ledger – the distributed ledger – that everyone looks at.

Quantum money solves the same problem much more directly. You don’t need a global ledger to track the history of ownership if the token himself it is physically uncopyable and can only be spent once.

• Blockchain secures transaction history in a ledger.
• Quantum Money ensures the token itself.

If each digital dollar has its own inherent physical security, the entire energy-intensive apparatus of a proof of work blockchain becomes redundant. Verification is a direct physical process, not a global consensus event.

A different philosophy: The centralized compromise

While quantum money could replace blockchain technology, it does not share its decentralized philosophy. Gilboa is quick to make this distinction.

“We are not solving the same problem,” he emphasized. “What we’re doing is not decentralized, so it’s not really a cryptocurrency analog in a strong sense.”

The Google model assumes a trusted central issuer, such as a bank, to create quantum tokens. However, it brilliantly uses physics to keep this problem honest.

The system is designed to provide a powerful privacy guarantee, preventing the bank from tracking its own currency. Users can join to do an “exchange test” on their quantum tokens.

“If they are not … identical, that means the bank could follow,” Gilboa said. Any attempt by the bank to secretly tag their money would be immediately revealed.

A glimpse of a distant future

This financial revolution will not happen tomorrow.

Gilboa stresses that the research is entirely theoretical and far beyond current capabilities.

“It assumes not only that you have a large fault-tolerant quantum computer, but also the ability to do quantum communication … another set of very difficult engineering challenges,” he said.

Even so, research is very important.

It shows that the defining technological solution of the last decade – the blockchain – is not the only answer to securing digital value. The brute force accounting of a distributed ledger could one day be replaced by the elegant and absolute laws of the quantum realm.

“It’s this crazy tool,” Gilboa concluded. “You can do all these wild things. It’s high risk, high reward — but that’s what makes it exciting.”